Today's internet equipment (modems, routers, firewalls etc) have some amount of buffers, the amount of memory has increased much faster than the bandwidth they serve, this might introduce significant network delay, and thus a bad user experience especially for real-time application such as video conferencing. Many of these real-time application have built various different delay sensing methods, but the issue is that when they compete with a protocol that only reacts to packet loss, they are loosing out and end up using less than their fair share of the network resources.